Legislation fixing systemic failures revealed after the Pike River mine tragedy is back in Parliament, unanimously passing its first reading.

The Health and Safety (Pike River Implementation) Bill is an "important part of the Government's commitment to the Pike River families" as it seeks to implement the recommendations of the Royal Commission on the Pike River Coal Mine Tragedy by the end of this year, Labour Minister Simon Bridges said.

The bill enables the transfer of relevant staff and assets from the Ministry of Business, Innovation and Employment to WorkSafe New Zealand - the Crown body which will be dedicated to health and safety - by its December start.

It will also strengthen the powers of health and safety representatives and allow for the industry-wide appointment of those representatives.

There are provisions however to ensure that they do not impede production unnecessarily.

The Engineering and Printing Manufacturers Union said they were concerned about the diluting of worker voices and said they would fight any movement to do that.

"There are concerns around the terminology but given the speed of the process we'd be fairly confident there'll be plenty of opportunity to overcome that," assistant national secretary Ged O'Connell said.

Bridges said it was a delicate balance between protecting workers and ensuring those privileges were not abused.

"The basic issue is we want health and safety representatives... to feel free to speak up to stop work in the interest of health and safety but of course just as in Australia we don't want to see that used for other reasons like wage disputes for example."

There would be levers in the legislation to ensure this did not happen, he said.

The bill also extends the coverage of the Mines Rescue Service to include underground mining and tunnels that are longer than 150 metres.

The introduction of the bill comes as public consultation is carried out on wider reform of mining regulations.

Earlier yesterday, Labour MP Darien Fenton raised concerns over what she said was the failure to appoint enough staff new to man the Health and Safety Inspectorate ahead of the July 1 deadline, claiming only 74 of 158 inspectors had been appointed.

Bridges, however dismissed the claims saying there will be at least 132 inspectors and managers and six chief inspectors from that date with an additional 15 appointed over the following fortnight.

Bridges said some former inspectors who had to reapply for their jobs had failed more stringent new standards and been reassigned elsewhere in the new ministry.